The present invention relates to devices for controlling a web in a printing press.
In the past, printing presses have had a suitable device to control the tension in a web, such as a dancer roll and associated tension detector, in the presence of power supplied to the press. Although such devices may cause sufficient control in the tension of the web under usual conditions, occasionally the press may be subjected to a power loss which renders such a tension control device inoperative and ineffective.
During the sudden power loss, the inertia of the rotating supply roll of the web renders the moving web into an uncontrolled condition, thus causing a possible breakage of the web, and possibly large slack portions of the web which may entangle in the press, thus causing secondary undesirable conditions in the press, which may cause damage to the press. Of course, even in the case of web breakage, when the power is again supplied to the press, the surplus portions of the web must be removed from the press, and the web must be again threaded through the press to continue printing of the web, thus causing inconvenience and loss of time to the operator of the press.